Everyone has a right to put forth rules in their own homes. But I disagree that this should be any kind of universal or general rule for Christians. I would find it ridiculous to have to wear a shirt in a pool, as if the very sight of my bare chest would scandalize everyone. No, it is natural and not inherently sinful in any way. In fact, if we were more mature, nudity would not be a problem, and in fact, it is not in other cultures. The problem is we sexualize everything.
I agree that, given the level of maturity in our society, both women and men should wear modest swimsuits, trunks, etc. But a man’s chest does not have the sexual connotation that woman’s chest has in our society. And I see no reason why men must wear shirts in a pool or beach for “modesty”. That to me is going to far and in fact, sexualizing and making taboo a perfectly non-sexual, normal thing.
The real world is full of temptation. To stay away from the beach because of temptation would be to deprive yourself of one of God’s creations due to undue fear. Yes, I have seen many women in “immodest” bikinis, etc… Maybe I have even felt lust for them… but I quickly push the thought away and enjoy the healthy joys of the beach with my friends. And frankly, I find that occasions of lust are few and far in-between if one is focused in the moment and enjoying the sun, the sand, the water and the company of friends. No sinfulness there.
We are not puritans.